FIG. 5 is a schematic sectional view of a tooth 51 of a motor core 50 described in JP 2004-242443 A. In FIG. 5, the motor core 50 is a dust core which is formed by compression molding of magnetic powder particles having an insulating film. The tooth 51 is formed to have an outer peripheral surface with a smooth curved surface. A resin is coated on the outer peripheral surface of the tooth 51 to form an insulating film layer 52, and a winding wire 53 is wound on the insulating film layer 52 around the whole circumference of the tooth 51.
With a motor core 50 having the above structure as described in JP 2004-242443 A, because the outer peripheral surface of the tooth 51 is formed to have a smooth curved surface, no one portion of the winding wire 53 is subjected to a particularly high surface pressure, and an insulating film covering the winding wire 53 does not frequently become damaged. Therefore, in a case where the very thin insulating film layer 52 is applied to the tooth 51 and the motor is used for a long time, short circuiting between the core line (copper line) of the winding wire 53 and the tooth 51 can be sufficiently prevented.
Because the outer peripheral surface of the tooth 51 is formed on the smooth curved surface, no gap is produced between the tooth 51 and the winding wire 53. Thus, the space for winding the winding wire 53 is increased, and an occupied area ratio of the winding wire can be increased by increasing the winding wire 53 or a flux amount can be increased by thickening the tooth 51. As a result, the motor output can be improved.
JP 2004-364402 A describes that a core which is provided with a coil and formed by compression molding of insulation-coated magnetic powder particles has an insulating film which is formed of insulating powder particles on a mounting surface where the coil is mounted.
JP 1-050730 A describes that an inorganic heat-resistant insulating layer of ceramic or the like is previously applied to a portion having slots in which a winding wire is incorporated or a portion where a winding wire and a stator are mutually contacted.
JP 9-149580 A discloses that the surface of an electric motor part formed of a plastic molded part is coated with a thin film of an inorganic material.
JP 2004-251412 A describes a rolling bearing having an insulating layer of a diamond like carbon layer.